Air bladder type vent valve for use in an hydraulic oil tank of an enclosed hydraulic transmission system

ABSTRACT

Air bladder type vent valve is disclosed having an air bladder fastened to the air vent of the hydraulic oil tank of an enclosed hydraulic transmission system, for example, hydraulic jack and suspended inside the hydraulic oil tank, and a fastening device, which affixes the air bladder to the periphery of the air vent in an airtight status to keep the inside space of the air bladder in air communication with the atmosphere so that the inside pressure of the hydraulic oil tank is maintained in balance with the atmosphere during the operation of the enclosed hydraulic transmission system to pump hydraulic fluid in and out of the hydraulic oil tank.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates generally to a hydraulic oil tank for an enclosed hydraulic transmission system and more specifically, to an air bladder type vent valve for use in an hydraulic oil tank that keeps the inside pressure of the hydraulic oil tank in balance with the atmospheric pressure.

(b) Description of the Prior Art

Due to the limitation of installation space and the consideration of cost, the hydraulic oil tank of an enclosed hydraulic transmission system, for example, hydraulic jack, has a limited size. During working, hydraulic fluid is pumped out of the hydraulic oil tank into the work chamber. At this time, a vacuum is produced in the hydraulic oil tank. The presence of the vacuum gives a barrier to the pumping action of the pump that pumps hydraulic fluid out of the hydraulic oil tank into the work chamber, thereby lowering the working efficiency of the pump. When the vacuum status of the hydraulic oil tank is increased, outside air may be sucked into the inside of the hydraulic oil tank. When air enters the hydraulic oil tank, it takes an equal volume of the inside space of the enclosed hydraulic transmission system and will not easily be expelled out of the hydraulic oil tank. In this case, the lifting rod of the enclosed hydraulic transmission system (hydraulic jack) cannot be returned to its former position. According to conventional designs, the work of expelling air out of the hydraulic oil tank is achieved manually.

There are air vents designed for use in the hydraulic oil tank of an enclosed hydraulic transmission system to keep the inside space of the hydraulic oil tank in balance with the atmosphere. However, because the inside space of the hydraulic oil tank is in communication with the atmosphere through the vent valve, hydraulic fluid may leaks out of the vent valve.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide an air bladder type vent valve for use in the hydraulic oil tank of an enclosed hydraulic transmission system, which automatically eliminates vacuum from the hydraulic oil tank, keeping the inside pressure of the hydraulic oil tank constantly in balance with the atmosphere.

To achieve this and other objects of the present invention, the air bladder type vent valve comprises a hydraulic oil tank installed in an enclosed hydraulic transmission system to hold a hydraulic fluid, the hydraulic oil tank having an air vent, and a vent valve mounted in the air vent for guiding in air from the atmosphere, wherein the vent valve comprises an air bladder suspended inside the hydraulic oil tank, the air bladder having a mouth connected to the air vent for guiding in outside atmospheric air, and fastening means affixing the air bladder to the periphery of the air vent in an airtight status to keep the inside space of the air bladder in air communication with the atmosphere. When hydraulic fluid is pumped out of the hydraulic oil tank, a corresponding volume of atmospheric air is sucked into the air bladder, keeping the inside pressure of the hydraulic oil tank in balance with the atmospheric pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing an air bladder type vent valve installed in the hydraulic oil tank of a hydraulic jack according to the present invention.

FIG. 2 is similar to FIG. 1 but showing the air bladder inflated.

FIG. 3 is an exploded view in an enlarged scale of a part of FIG. 1, showing the mounting structure of the air bladder type vent valve according to the present invention.

FIG. 4 is an assembly view in an enlarged scale of FIG. 3.

FIG. 5 is a sectional view of an alternate form of the air bladder, showing ribs formed integral withy the inside wall of the mouth of the air bladder according to the present invention.

FIG. 6 is a sectional view taken along line A-A of FIG. 5.

FIG. 7 is a schematic drawing showing the effect of the ribs of the air bladder according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an air bladder type vent valve installed in an enclosed hydraulic transmission system, for example, a hydraulic jack 10. As illustrated, the hydraulic oil tank 1 of the hydraulic jack 10 has an air vent 11. An air bladder 2 is fastened to the air vent 11 and suspended inside the hydraulic oil tank 1. The inside space 21 of the air bladder 2 is in air communication with the atmosphere. Normally (non-operative status of the hydraulic jack 10), the air bladder 2 is kept in the status shown in FIG. 1. When the hydraulic jack 10 is started (for example, when the lifting the piston rod 101 of the hydraulic jack 10), the pump rod 102 of the hydraulic jack 10 is moved upwards to suck hydraulic fluid 3 from the hydraulic oil tank 1 into the pump chamber 103, and then the pump rod 102 of the hydraulic jack 10 is lowered to squeeze hydraulic fluid 3 out of the pump chamber 103 into the work chamber 104 to lift the piston rod 101 for one stroke. This pumping action is repeated again and again to lift the piston rod 101 to the desired elevation. When pumping hydraulic fluid 3 out of the hydraulic oil tank 1 into the pump chamber 103, a vacuum is produced in the hydraulic oil tank 1, and a corresponding volume of atmospheric air automatically passes into the air bladder 2 to inflate the air bladder 2 (see FIG. 2), keeping the inside pressure of the hydraulic oil tank 1 in balance with the atmospheric pressure. Because the inside pressure of the hydraulic oil tank 1 is maintained in balance with the atmospheric pressure, the pump rod 102 can be moved to the full extent upon each pumping action. During each down stroke of the pump rod 102, hydraulic fluid 3 is returned from the pump chamber 103 to the hydraulic oil tank 1 to expel a corresponding volume of air out of the air bladder 2 into the atmosphere, keeping the inside pressure of the hydraulic oil tank 1 in balance with the atmospheric pressure.

The air bladder 2 is made of a soft airtight material that is capable of isolate hydraulic fluid 3, preventing a leakage. For example, the air bladder 2 can be made of nylon film. Alternatively, elastic airtight material such as rubber material may be used for making the air bladder 2.

The air bladder 2 is fastened to the inside wall of the air vent 11 in an airtight status. According to the embodiment shown in FIGS. 3 and 4, an inner mounting ring 111 and an outer mounting ring 112 are fastened to the inside wall of the air vent 11 to secure the air bladder 2 to the inside wall of the air vent 11 in an airtight status, keeping the inside space of the air bladder 2 in air communication with the atmosphere. The inner mounting ring 111 can be a rubber seal ring that prevents leakage.

According to the embodiment shown in FIGS. 5˜7, the air bladder 2 has ribs 22 spaced around the inside wall of the mouth thereof to support the mouth in an open status for air communication between the inside space 21\of the air bladder 2 and the atmosphere. An annular rib may be formed integral with the inside wall of the mouth of the air bladder 2 instead of the ribs 22.

A prototype of air bladder type vent valve has been constructed with the features of FIGS. 1˜7. The air bladder type vent valve functions smoothly to provide all of the features discussed earlier.

Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims. 

1. An air bladder type vent valve comprising a hydraulic oil tank installed in an enclosed hydraulic transmission system to hold a hydraulic fluid, said hydraulic oil tank having an air vent, and a vent valve mounted in said air vent for guiding in air from the atmosphere, wherein said vent valve comprises an air bladder suspended inside said hydraulic oil tank, said air bladder having a mouth connected to said air vent for guiding in outside atmospheric air, and fastening means affixing said air bladder to the periphery of said air vent in an airtight status to keep the inside space of said air bladder in air communication with the atmosphere.
 2. The air bladder type vent valve as claimed in claim 1, wherein said air bladder is made of a soft airtight material.
 3. The air bladder type vent valve as claimed in claim 1, wherein said air bladder is an inflatable bag made of a flexible airtight material.
 4. The air bladder type vent valve as claimed in claim 1, wherein said fastening means comprises an outer mounting ring sealed to said air vent, and an inner mounting ring fastened to said outer mounting ring to seal the periphery of the mouth of said air bladder to said outer mounting ring.
 5. The air bladder type vent valve as claimed in claim 4, wherein said inner mounting ring is a rubber seal ring.
 6. The air bladder type vent valve as claimed in claim 1, wherein said air bladder has at least one rib formed integral with an inside wall of said mouth. 